Aluminum is one of the most common elements on earth, and one of the most common ingredients in antiperspirants. For years, online health forums and wellness communities have raised concerns that daily aluminum exposure, particularly from underarm products, could contribute to breast cancer. A new systematic review published in the Journal of Trace Elements in Medicine and Biology takes the most comprehensive look to date at what the clinical evidence actually shows and finds that the picture is far more complicated than the headlines suggest.

‍Study Overview

Researchers at the University of Strasbourg conducted a systematic review of 19 studies examining the relationship between aluminum exposure and breast cancer risk. The review, guided by PRISMA guidelines, included cohort studies, case-control studies, and meta-analyses published through November 2022. Six studies assessed the connection between antiperspirant or deodorant use and breast cancer incidence. Thirteen additional studies measured aluminum concentrations directly in breast tissue, nipple aspirate fluid, urine, and hair samples from women with and without breast cancer.

Key Findings

The results across studies were mixed and often contradictory.

• Among the six studies on antiperspirant and deodorant use, most found no statistically significant association with breast cancer risk, including the largest, best-controlled studies. One small study from Iraq found the opposite: women who used antiperspirants were actually less likely to develop breast cancer.
• Two studies suggested that beginning antiperspirant use before age 30, particularly multiple times daily, was associated with an elevated risk or earlier age at diagnosis. However, both involved fewer than 20 patients, limiting any meaningful conclusions.
• Among studies measuring aluminum in breast tissue, results were split. Some found higher aluminum concentrations in tumor tissue compared to healthy tissue; others found no significant difference. Studies also examined whether aluminum concentrates more heavily in the outer breast region closest to the underarm (where antiperspirants are applied)  but those findings were equally divided, with two studies confirming higher levels there and two finding no regional difference at all. Separately, studies measuring aluminum in nipple aspirate fluid, a natural secretion that can reflect the breast's internal environment, did find elevated levels in women with breast cancer, along with higher markers of oxidative stress and inflammation.
• Lab studies on cell lines told a different story. In vitro research showed that aluminum can cause DNA damage, disrupt estrogen receptor signaling, compromise DNA repair genes including BRCA1 and BRCA2, and increase the invasive behavior of breast cancer cells. Mouse models showed tumor formation and lung metastases following chronic aluminum exposure, with no tumors developing in unexposed control animals. Researchers are careful to note, however, that laboratory findings don't automatically translate to human risk.

Why It Matters

Breast cancer is the most common cancer worldwide, representing nearly a quarter of all new cancer diagnoses in women. Because known risk factors (genetics, hormone exposure, age) account for fewer than 25% of cases, identifying environmental contributors is a legitimate and important public health question. Aluminum, classified as a metalloestrogen for its ability to mimic estrogenic activity in the body, has been a particular point of concern given how widely antiperspirants are used, sometimes from a young age.

The researchers highlight several important distinctions that are often blurred in both the scientific literature and public discussion. Antiperspirants and deodorants are not the same product. Antiperspirants contain aluminum salts that physically block sweat glands and are regulated as drugs. Deodorants contain no aluminum and work through fragrance and antimicrobials. The review finds no clinical evidence implicating aluminum-free deodorants in breast cancer risk.

The authors also note that aluminum's role, if any, remains unclear: it may be a contributing factor to tumor development, a biomarker of existing tumor activity, or simply a consequence of increased blood supply to highly vascularized tumors.

Takeaways

This review doesn't definitively link aluminum to breast cancer, and further research studies have only reinforced the lack of a clear clinical association. That said, reducing unnecessary exposure to aluminum remains a reasonable, low-effort precaution.

• Choose aluminum-free deodorants when possible, particularly if you use underarm products daily or began using them before adulthood.
• Avoid applying antiperspirants to broken or irritated skin, which may increase absorption. France's health safety agency (AFSSAPS) has specifically recommended this, along with capping aluminum content in antiperspirants at 0.6%.
• Be aware of other aluminum sources in daily life; food cooked or stored in aluminum foil or cans, aluminum-based antacids, and certain cosmetics all contribute meaningfully to overall exposure.
• Don't rely on internet searches alone for guidance on breast cancer risk. A 2018 analysis found deodorants were the second most-searched environmental risk factor for breast cancer online, but online information often overstates the certainty of the link.

Read the Study: Moussaron A, et al. Correlation between daily life aluminium exposure and breast cancer risk: A systematic review. Journal of Trace Elements in Medicine and Biology. 2023.